14(√6+√2)
14(√6−√2)
−14(√6−√2)
−14(√6+√2)
Correct answer is D
cos165=−cos(180−165)=−cos15
cos15=cos(45−30)
cos(x−y)=cosxcosy+sinxsiny
cos(45−30)=cos45cos30+sin45sin30
= (√22)(√32)+(√22)(12)
= 14(√6+√2)
∴
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